Testimony during the six-month "death-squad" trial that ended yesterday recalled an era when Prince George's County police were often accused of taking a cavalier attitude toward law enforcement. The police were said to be feared, and citizens groups frequently complained about unfair and brutal treatment at the hands of officers.

Whether such an image--prominent during the 1960s and early 1970s--was deserved or not, there have been some noticeable changes in the police department since then. Citizen complaints of brutality have decreased sharply since the mid-1970s. At the same time, the number of black officers on the force has risen substantially since the first two blacks were hired in 1967.

During the 1970s, complaints of brutality and racism led to investigations of the police department by the FBI and the county Human Relations Commission. John Rhoads, police chief from 1975 to 1979, said recently that "there were heavy-handed tactics used against blacks."

Public pressure prompted Rhoads to hire a civilian, Thomas Davis, to teach human relations at the police academy in 1976. Davis, a retired black Air Force officer was appointed a deputy chief in 1981 by the current chief, John E. McHale Jr.

According to other officers and Davis himself, Davis' appointment initially raised the ire of many policemen. But his racial awareness program made an important difference with officers on the street, according to Rhoads. The new posture of the department was, "We can't tell you how to think, but we can tell you how to act," Rhoads said. In addition, officers who were accused of misconduct were much more likely to be investigated by the commission and the police Internal Affairs Division, according to Davis.

Deputy Chief Rice Turner, now in charge of patrol officers, and others say that as police made more of an effort to understand community concerns, there was a decrease in the number of citizen complaints of police brutality or excessive force.

According to Capt. Milton Crump of internal affairs, excessive force complaints went from 15 in 1970 to a high of 83 in 1975 and have been around 20 since then. He said that 36 excessive force complaints were filed in 1982, but that in only a handful of these complaints was there a preponderance of evidence that an officer did something wrong.

Although comparative figures were not readily available yesterday from the Human Relations Commission, which also investigates complaints against the police, agency director William Welsh said that complaints have declined from a peak in 1975.

In 1975, Rhoads began an aggressive push to hire blacks that included pirating black officers from the District and the Maryland State Police. For the last few years, the police department has attempted to assemble recruit classes that are half black and half white. As of last January, there were 145 blacks on the department--about 15 percent of the 900-member force. The county population is about 37 percent black.

Still, the "tough guy" image lingers in the department, says Capt. George Robinson, a 17-year veteran who runs the Bowie station. "We have hired and kept on brutal people," Robinson says. But younger officers hired in recent years, he added, are generally better-educated and have grown up in a more integrated and tolerant society.